Traditionally, parametric speech coding methods make use of the redundancy inherent in the speech signal to reduce the amount of information to be sent and to estimate the parameters of speech samples of a signal at short intervals. This redundancy can arise from the repetition of speech wave shapes at a quasi-periodic rate and the slow changing spectral envelop of speech signal. The redundancy of speech wave forms may be considered with respect to different types of speech signal, such as voiced and unvoiced. For voiced speech, the speech signal is substantially periodic. However, this periodicity may vary over the duration of a speech segment, and the shape of the periodic wave may change gradually from segment to segment. A low bit rate speech coding could significantly benefit from exploring such periodicity. The voiced speech period is also called pitch, and pitch prediction is often named Long-Term Prediction (LTP). As for unvoiced speech, the signal is more like a random noise and has a smaller amount of predictability.